It is mainly artificial. A bit like the zoning codes in the US I think.
There is property where you can build a proper house and live there (requirement is, that there is infrastructure, like water and electricity). Then there are gardens, where maybe a small cabin is allowed (but you may not officially live there). And then there is everything else, where you normally cannot build anything.
I don't think there are any wooded lots in Germany, at least not in the way you're thinking. If your lot is at least a quarter acre big and some 30 feet wide, it counts as a forest.
A quarter of an acre of trees is a "forest"? Whoa. As someone who grew up amidst a thousand miles of trees, I shall be laughing for a week to myself over such an idea.
Of course, your typical forest is bigger than that even in Germany. This is the minimum size a piece of land with trees on it has to have to be considered a forest by law.
Moreover because most of Germany’s “forests” are man-made… are they not mostly “wooded lots”? The distinction maybe arises from green space preservation policies?
There is property where you can build a proper house and live there (requirement is, that there is infrastructure, like water and electricity). Then there are gardens, where maybe a small cabin is allowed (but you may not officially live there). And then there is everything else, where you normally cannot build anything.